Rational constructing 2D/3D p-n heterojunctions to modulate hydrogen evolution efficient pathways for enhances photocatalytic hydrogen production

Heterojunctions within the regions of two different semiconductor exhibit lower charge transfer barriers, thereby facilitating efficient carrier transport and separation. Thus, an essential approach to enhancing the photocatalytic hydrogen evolution performance of g-CN lies in investigating methods to improve the carrier migration rate of g-CN, starting from its carrier transport properties. By anchoring sea urchin-like CuCoO onto the surface of porous lamellar g-CN to form a p-n heterojunction, rapid separation of photo-generated electron-hole pairs are achieved. It is noteworthy that, the Fermi level of g-CN is higher than that of CuCoO, due to the Fermi level of the n-type semiconductor being close to the conduction band and that of the p-type semiconductor being close to the valence band. The Fermi level effect between the two results in electrons on g-CN being more likely to transfer to CuCoO until equilibrium is reached. Consequently, an internal electric field from g-CN to CuCoO is formed, promoting easier electron transfer from the conduction band of CuCoO to that of g-CN, while holes from the valence band of g-CN are more prone to transfer to the valence band of CuCoO, ultimately forming the p-n heterojunction and enhancing the carrier migration rate of g-CN. Upon optimization, the hydrogen evolution activity of the composite photocatalyst g-CN/CuCoO-25 % reaches 2843.38μmol gh, surpassing that of g-CN (18.93μmol gh) and CuCoO (32.54μmol gh) by 150 times and 87 times, respectively, demonstrating outstanding photocatalytic performance. This study provides a feasible and effective strategy for designing p-n heterojunctions to promote photocatalytic hydrogen production.